Role of claustrum in incubation of opioid seeking after electric barrier-induced voluntary abstinence in male and female rats

We previously reported that ventral subiculum (vSub) activity is critical to incubation of oxycodone seeking after abstinence induced by adverse consequences of drug seeking. Here, we studied the role of claustrum, a key vSub input, in this incubation. We trained male and female rats to self-administer oxycodone for 2 weeks and then induced abstinence by exposing them to an electric barrier for 2 weeks. We used retrograde tracing (cholera toxin B subunit; CTb) plus the activity marker Fos to identify projections to vSub activated during ‘incubated’ relapse (abstinence day 15). We then used muscimol+baclofen (GABAa+GABAb receptor agonists) reversible inactivation to determine causal role of claustrum in incubation and the behavioral and anatomical specificity of this role. We also used muscimol+baclofen in an anatomical disconnection procedure to determine the causal role of claustrum-vSub connections in incubation. Finally, we analyzed an existing functional MRI dataset to determine if functional connectivity changes in claustrum-related circuits predict incubation of oxycodone seeking. Claustrum neurons projecting to vSub were activated during relapse tests after electric barrier-induced abstinence. Inactivation of claustrum but not areas dorsolateral to claustrum decreased incubation of oxycodone seeking after electric barrier-induced abstinence; claustrum inactivation had no effect on incubation after food choice-induced abstinence. Both ipsilateral and contralateral inactivation of claustrum-vSub projections decreased incubation after electric barrier-induced abstinence. Functional connectivity changes in claustrum-cortical circuits during electric barrier-induced abstinence predicted incubated oxycodone relapse. Our study identified a novel role of claustrum in relapse to opioid drugs after abstinence induced by adverse consequences of drug seeking. Significance statement We recently reported that vSub is critical to incubation of oxycodone craving after abstinence induced by adverse consequences of drug seeking. Here, we first showed that claustrum projections to vSub are active during tests for incubation of oxycodone seeking after electric barrier-induced abstinence. Next, we used pharmacological inactivation to test the causal roles of claustrum and its anatomical connections with vSub in incubation. Using an existing functional MRI dataset, we also tested if functional connectivity changes in claustrum-related circuits predicted ‘incubated’ oxycodone relapse after electric barrier-induced abstinence. Our data suggest that claustrum- and claustrum-related circuits contribute to relapse after voluntary abstinence induced by adverse consequences to drug seeking but not abstinence induced by availability of alternative non-drug rewards.